1. Field of the Invention
The present invention relates to an antenna device used in portable communication devices. The present invention is more particularly related to an antenna device used in a portable communication device that can be mounted to a circuit board of the portable communication device, and provides a maximum gain in a direction not toward a user of the portable communication device.
2. Description of the Related Art
An antenna device which is small-sized, having high gain, fabricated at low cost and easy to mount has been long needed as an antenna device for use in portable communication devices. Unfortunately, conventional linear antennas such as dipole antennas, monopole antennas, etc., are of large volume which hampers downsizing of a communication device. Furthermore, such antennas are not easily mounted to a main body of a communication device and therefore a communication device equipped therewith is difficult to use and less portable.
Several antennas have been proposed to resolve such problems.
FIG. 65 is a perspective view showing an antenna device proposed in Japanese Unexamined Patent Publication No. JP-A-7-235825.
A radiating conductor film 992 is formed on the entire upper face of a dielectric substrate 991 constituting an antenna device 990. A grounding film 993 is formed on the lower face of the dielectric substrate 991. The grounding conductor film 993 has a shape where a portion of one of two short sides is notched and an exciting conductor film 994 is formed at the notched portion. A feed electrode 995 is formed at a side face of the dielectric substrate 991 and the feed electrode 995 is connected to the exciting conductor film 994. Ground electrodes 996 and 997 are formed to interpose the feed electrode 995 at the side face of the dielectric substrate 991 and the ground electrodes 996 and 997 are connected to the grounding conductor film 993. Further, a through hole 998 having a conductor at an inner wall thereof is formed in the dielectric substrate 991. And the radiating conductor film 992 and a front end portion of the exciting conductor film 994 are electrically connected by the through hole 998.
The antenna device 990 constituted as described above is mounted on the surface of a circuit board incorporated in the main body of a communication device, high frequency power is supplied from the main body of the communication device to the radiating conductor film 992 via the feed electrode 995, the exciting conductor film 994 and the through hole 998. Electromagnetic waves are radiated to air from the radiating conductor film 992 by an electromagnetic coupling between the exciting conductor film 994 and the radiating conductor film 992.
FIG. 66 is a perspective view showing an antenna device proposed by Japanese Unexamined Patent Publication No. JP-A-7-283639.
A through hole 1102 constituting a radiating conductor film at its inner wall is formed in a dielectric base body 1101 constituting an antenna device 1100. A surface electrode 1103 is formed on the surface of the dielectric base body 1101 and a connector external conductor plate 1104 is attached to the rear face thereof. The surface electrode 1103 and the connector external conductor plate 1104 are electrically connected by the radiating conductor film formed on the inner wall of the through hole 1102. Further, a coaxial connector 1105 is attached to a face of the connector external conductor plate 1104 opposed to a face thereof on which the dielectric base body 1101 is attached. An external conductor and an internal conductor of the coaxial connector 1105 are electrically connected to the connector external conductor plate 1104 and the radiating conductor film in the through hole 1102, respectively.
The antenna device 1100 constituted as described above is arranged to the main body of a communication device by connecting the coaxial connector 1105 to a connector installed to the main body of the communication device. High frequency power is supplied from the main body of the communication device to the antenna device 1100 via the coaxial connector 1105 and electromagnetic waves are radiated from the radiating conductor film formed on the inner wall of the through hole 1102.
FIG. 67 is a perspective view showing an antenna device proposed by Japanese Unexamined Patent Publication No. JP-A-7-221537.
A through hole 1212 constituting a radiating conductor film at its inner wall is formed in a dielectric substrate 1211 constituting an antenna device 1210 in a direction of long side of the dielectric substrate 1211. A side face electrode 1213 is formed on an entire face of an end face of the dielectric substrate 1211, a feed electrode 1214 is formed at a central portion of the other end face and the side face electrode 1213 and the feed electrode 1214 are electrically connected by the radiating conductor film formed on the inner wall of the through hole 1212. Further, side face electrodes 1215 and 1216 are formed to interpose the feed electrode 1214 on the other end face of the dielectric substrate 1211 where the feed electrode 1214 is formed.
The antenna device 1210 constituted as described above is mounted to a circuit board incorporated in the main body of a communication device, high frequency power is supplied from the main body of the communication device to the antenna device 1210 via the feed electrode 1214 and electromagnetic waves are radiated from the radiating conductor film at the inner wall of the through hole 1212.
According to the antenna device 990 shown by FIG. 65, the frequency band of electromagnetic waves must be narrowed to enhance gain. Therefore, when frequencies of electromagnetic waves for transmission and receiving are different from each other as in a portable telephone, it is difficult to use the antenna device 990 as an antenna both for transmission and receiving.
The antenna devices 1100 and 1210 shown by FIG. 66 and FIG. 67, are nondirectional in respect of a face expanding perpendicularly to a direction of extending the through hole where the radiating conductor film is formed. When such antenna devices are mounted to, for example, a portable telephone, a portable telephone generally transmits and receives vertically polarized electromagnetic waves and therefore, the antenna device is mounted to the main body of a portable telephone such that a direction of extending the through hole coincides with a longitudinal direction of the main body of the portable telephone.
When a person actually uses a portable telephone mounted with such an antenna device, since the antenna device is nondirectional in respect of a face perpendicular to a direction of extending the through hole, a portion of electromagnetic waves transmitted from the antenna device is radiated toward a human body. The electromagnetic waves radiated toward the human body are not used in communication.